The present invention generally relates to a signal processor. More particularly, the present invention relates to a signal processor for processing a played-back signal from a recording medium such as a magnetic disk and an optical disk.
There is a variation between manufactured play-back apparatuses for a magnetic disk and an optical disk in terms of the capability (quality) of accurately playing back data recorded on the disk. Accordingly, the play-back apparatuses for a magnetic disk and an optical disk have a function to evaluate the quality of the apparatus. If the quality of the apparatus is low, various adjustments are made in order to improve the quality. For example, the quality of the apparatus is evaluated and adjustments of the apparatus are made if the apparatus gets out of order during inspection before shipment, or after shipment.
One example of a method for evaluating the quality of the play-back apparatus is to measure the bit error rate (bER) of the played-back data and evaluate the quality of the play-back apparatus by using the measured bit error rate as a quality value. The quality value obtained by this method is reliable as the data which most strongly correlates with a substantial quality index of the play-back apparatus. However, this method is not practical because it is difficult to process data in real time and a large circuit scale is required in order to deal with a large amount of data.